From lovely Rome mum brought back souvenir (6)
I believe the answer is:
memory
'souvenir' is the definition.
(thesaurus)
'from lovely rome mum brought back' is the wordplay.
'from' says the answer is hidden in the clue.
'brought back' is a reversal indicator.
'yromem' can be found hidden inside 'lovely rome mum'.
'yromem' in reverse letter order is 'MEMORY'.
(Other definitions for memory that I've seen before include "Mental retention" , "Power of recall" , "See 23" , "Something recalled; part of computer" , "(Computer) data store" .)